As demonstrated in U.S. patent application Ser. No. 522,571, assigned to the assignee of this invention, the wear life of a substantially dense nonoxide ceramic, which is movingly interfaced at high temperatures or speed with a metal (of the type that forms a compound containing a metal oxide under the temperature conditions prevailing at the interface with the ceramic member), can be substantially improved by removing oxygen from between the ceramic member and the metal during such interfacing. In the referenced patent application, it was stated that a stream of inert gas, preferably nitrogen, should be directed at the cutting interface to reduce the presence of oxygen there, by at least 60% and optimally 100%. However, the ability to exclude oxygen at the higher percentages in this range is not easily obtained. If the flow of inert gas is from a source such as a nozzle, and is relatively slow so as not to consume a high quantity of the inert gas during the period of cutting, the rotation of the workpiece being cut sets up a boundary layer wind which blows the inert gas away from the workpiece surface, allowing oxygen or air to reach the workpiece in undesirable amounts. If the flow of inert gas is increased in intensity, such as by use of a needle-like jet, the suction created behind the high speed gas jet brings in oxygen or air, again exposing the workpiece to undesirable quantities of oxygen or air.
What is needed is an apparatus and method by which an inert atmosphere may be flowed into place at the interface of a cutting tool and rotating workpiece without eventual substantial displacement by air or an oxygen bearing gas.